The decline of the high street that David Cameron asked TV's Queen of Shops, Mary Portas, to reverse has been a death much foretold. Even the precise manner of the dying was anticipated. In 2001 the New Economics Foundation produced the first of its reports about the alarming rate at which local shopping centres were being hollowed out by out-of-town developments and the unchecked march of big retailers. Its subsequent reports on Clone Town Britain pointed out that in times of recession, large chains tend to pull out of high streets faster than small independents who hold out longer, using their own savings and local goodwill to hang on.

Not much was done about the warnings, and now Portas, whose review is published today, finds British high streets are indeed at death's door, unlikely to survive without urgent action. Portas is famous for her forthright "get your act together" approach to advising small businesses, and Cameron may have hoped that one of our most high-profile retail celebrity experts could come up with solutions; a dramatic quick fix in the style of a TV series rescue. In their heartlands of rural England's market towns, rank-and-file Tories are distressed by the loss of high street centres and the social fabric that used to accompany them, so it is a popular cause. But it will take a little more to bring the patient back to life, if it is not too late already.

Portas has produced a reasonable analysis of the recent pathology of the disease, if not the deeper aetiology: supermarkets were allowed to get too big thanks to planning laws that were too relaxed. She might have added that it was also a result of competition laws that were too narrow and allowed monopolistic concentrations of power to emerge; and also local authorities that were too weak to enforce the laws big retailers routinely chose to break, such as those on Sunday trading, or expansion of their floor area beyond their planning permissions.

High streets have failed to adapt to changes in the pattern of shopping as they came under threat not just from big shed supermarkets but also the rise of internet shopping and changes in working patterns. These are structural changes in the nature of retail that will not be unwound. Portas was never likely to want them to go into reverse anyway. She is a great marketeer, and although she has attacked big supermarkets for the damage they have done to high streets in the past, she has done her own bit to promote the mega shopping mall and big chains. Her company, Yellow Door, promotes big chains such as Oasis and the mega shopping malls owned by the Westfield Group.

Portas makes some sensible suggestions: freeing local authorities so they can use business rates to attract new shops; making it easier to set up markets; and allowing changes of use when properties stand empty. But these are mere plasters that will not address the structural problems; ultimately, this exercise looks like the Tories wanting to have their cake and eat it.

The stripped down national planning policy framework from the Department for Communities and Local Government removes much of the key wording that might protect town centres. Gone is the explicit reference to brownfield sites being used first, which made sure that re-using space at the centre took precedence over other development. There is now a presumption in favour of "sustainable development" – but sustainable is no longer clearly defined as what is socially and environmentally sustainable, instead sliding into what is economically sustainable: in other words, anything goes.

Moreover, the ability of local people to challenge planning permissions they object to is undermined. Portas calls for the wording to be toughened up, but here she is up against the chancellor, George Osborne, who has talked of removing the planning obstacles to growth. Portas also calls for lower parking charges, but cuts to local authority budgets have forced them to push up town centre parking fees as a way of collecting revenue.

The irony is that the economic climate might start pushing people back into town centres when it is all but too late. The out-of-town big retail model, where leisure becomes shopping, is based on a cheap oil economy. But now the cost of sourcing globally and sending goods in circles through distribution centres up and down motorways is going up dramatically, feeding inflationary pressure. With petrol prices soaring and motorists feeling the pain at the pump, more people are talking about driving less. Giant shopping malls are the incarnation of the debt-fuelled, consumption-led growth that got us in to such trouble. Perhaps this is the mixed high street's best hope.